How to Check If an Array Contains an Element in JavaScript

Here are five ways to check if an array contains an element in JavaScript:

1. Using array.includes() method
2. Using array.indexOf() method
3. Using array.some() method
4. Using the array.find() method
5. Using the array.findIndex() method

Method 1: Using the Array.includes()

The includes() method is used to check whether an array contains a specified element. 

Example

const main_array = [11, 21, 18, 19, 46];

console.log(main_array.includes(19))

Output

true

That means 19 is there in the main_array. Now, let’s see a scenario where an array does not contain an element.

const main_array = [11, 21, 18, 19, 46];

console.log(main_array.includes(30))

Output

false

Method 2: Using the Array.indexOf() method

The indexOf() method is used to find the index of the first occurrence of a specified element in an array. It can help you determine if an array contains an element or not.

Example

const main_array = [11, 21, 18, 19, 46];

const index = main_array.indexOf(19);

console.log(index)

Output

3

You can see that element 19 exists on the 3rd index of the array.

Let’s check a scenario where an element does not exist in the array.

const main_array = [11, 21, 18, 19, 46];

const index = main_array.indexOf(30);

console.log(index)

Output

-1

That means an array does not contain an element. It returns -1 when it cannot find an element in the array.

Method 3: Using the Array.some() method

The some() method is a built-in function used to check if at least one element in an array passes a test implemented by a provided function.

Example

const main_array = [11, 21, 18, 19, 46];

const isArrayContains = main_array.some(item => item === 19);

console.log(isArrayContains)

Output

true

Let’s check a scenario where an array does not include an element.

const main_array = [11, 21, 18, 19, 46];

const isArrayContains = main_array.some(item => item === 30);

console.log(isArrayContains)

Output

false

Method 4: Using the Array.find() method

The find() method is used to get the value of the first element in an array that satisfies a given condition.

Example

const main_array = [11, 21, 18, 19, 46];

const isArrayContains = main_array.find(item => item === 19);

console.log(isArrayContains)

Output

19

If the array does not contain the element, it returns undefined.

const main_array = [11, 21, 18, 19, 46];

const isArrayContains = main_array.find(item => item === 30);

console.log(isArrayContains)

Output

undefined

Method 5: Using the Array.findIndex() method

The findIndex() method retrieves the index of the first element in an array that satisfies a given condition.

Example

const main_array = [11, 21, 18, 19, 46];

const isArrayContains = main_array.findIndex(item => item === 19);

console.log(isArrayContains)

Output

3

If the element does not exist in the array, the method returns -1 as an output.

const main_array = [11, 21, 18, 19, 46];

const isArrayContains = main_array.findIndex(item => item === 30);

console.log(isArrayContains)

Output

-1

Krunal

Krunal Lathiya is a seasoned Computer Science expert with over eight years in the tech industry. He boasts deep knowledge in Data Science and Machine Learning. Versed in Python, JavaScript, PHP, R, and Golang. Skilled in frameworks like Angular and React and platforms such as Node.js. His expertise spans both front-end and back-end development. His proficiency in the Python language stands as a testament to his versatility and commitment to the craft.